1. Field of the Invention
The present invention relates to a gene necessary for biosynthesis of UK-2 which is a compound useful for rice blast control agents and the like (hereinafter referred to as a “UK-2 biosynthetic gene”) and a method for improving UK-2 productivity. More specifically, the present invention relates to a UK-2 biosynthetic gene, a vector in which the UK-2 biosynthetic gene is inserted, a transformant in which the vector is introduced, a method for determining UK-2 productivity by detecting the presence of the UK-2 biosynthetic gene, a bacterium in which the presence of the UK-2 biosynthetic gene is detected by the method, a bacterium comprising the UK-2 biosynthetic gene inserted in a genome thereof, a bacterium in which one or two or more copies of the UK-2 biosynthetic gene are present per cell, and methods for producing UK-2 and a UK-2A derivative by utilizing these bacteria and so forth.
2. Related Background Art
UK-2 is a compound produced as a secondary metabolite by actinobacteria, and shows strong antifungal actions similar to antimycin against various fungi including filamentous fungi and yeasts. Further, since having low cytotoxicity to culture cells, UK-2 has been found to be useful for rice blast control agents, agricultural and horticultural fungicides, and medical antifungal agents (Japanese Examined Patent Application Publication No. Hei 07-233165 and International Publication No. WO1999/11127). Moreover, it has been revealed that there naturally exists four analogues, UK-2A to D, based on the difference in structure of their side chains (Ueki M., et al., Journal of antibiotics, Jul. 25, 1996, vol. 49, no. 7, pp. 639 to 643).
UK-2 is produced by culturing actinobacteria (bacteria and the like belonging to the genus Streptoverticillium) and then collecting UK-2 therefrom. However, generally, the amount of UK-2 (all UK-2 factors) produced by microorganisms isolated from nature is very small. Accordingly, in order to use the target (UK-2) industrially at low cost, the productivity has to be improved.
The productivity of the target is improved through investigations on the methods for culturing the microorganisms producing the target, investigations on the medium components, improvement in fermentation conditions by addition of the precursor, and improvement in the bacterial strain utilizing ultraviolet irradiation- or chemical mutagen-induced mutation. Furthermore, in addition to these methods, the productivity has been improved recently by utilizing gene recombination.
A general method for improving the productivity by gene recombination is that including the enhancing of expression of a gene necessary for biosynthesis of the target. For example, International Publication No. WO2001/018179 discloses that this method improves the productivity of μF-1022 in Agonomycetales.
However, when this method is utilized, it is essential to isolate the gene necessary for biosynthesis of the target or the gene synthesized using known techniques, and also to establish the transformation method for microorganisms producing the target (producing microorganisms). Since the UK-2 biosynthetic gene is yet to be elucidated, the transformation using the UK-2 biosynthetic gene cannot be performed. The productivity cannot be improved by gene recombination.